The present invention relates in general to magnetic tape cassettes and, more particularly, to a novel cassette having a structure including an improved means for selectively controlling the erase and record functions of a recording apparatus in which it is employed.
Frequently, after information has been recorded on a cassette tape, it is necessary or otherwise desirable to insure that the recorded material is preserved and will not be lost or destroyed in an inadvertent erasure or an inadvertent recording over of the pre-recorded material during a subsequent play-back or other processing of the tape. As a consequence, to preserve important recordings, cassette recorders and other tape processing equipment from the outset have been provided with an internal mechanism for sensing the presence of a cavity in a cassette which, when present, serves to inhibit the erase and recording functions of the apparatus. This inhibiting action occurs notwithstanding that the external and other controls on the apparatus are properly set to perform the function.
In the fabrication of a cassette, which generally involves molding the majority, if not all of the parts, the aforementioned cavity is molded in a wall of the cassette body member. To permit an initial recording of the cassette, a removable chip of the material used in molding the body member is molded also in a position to block access to the cavity. By so closing off the cavity, the recording circuits in the recording apparatus are prevented from being inhibited by the sensing mechanism, and the cassette tape may be recorded. Thereafter, if it is desired to preserve the material recorded on the tape, the chip is simply removed, opening the cavity to the cavity sensing mechanism.
If, subsequently, the necessity for preserving the recorded material ceases to exist and it is desired that the cassette be used again for the recording of fresh material, some means or other must be used for closing the cavity to the sensing mechanism.
Heretofore, various methods and apparatus have been proposed and used for this purpose. In some cases, masking, cellophane and other similar types of tape have been employed. When so used, the tape is simply placed over the entrance to the cavity and stuck to the sides of the cassette body. In other cases, removable plugs have been employed to fill the cavity.
In either instance, these prior known methods and means for closing the cavity have proved to be less than satisfactory. In the use of tape to close the cavity, there remains the possibility that the tape will loosen and fall into the recording apparatus or otherwise foul and interfere with its operation. Additionally, tape is subject to being perforated by the sensing mechanism. Should this occur during the making of an important recording, the resulting activation of the sensing mechanism and inhibiting of the recording circuits could result in the loss of important information. In such a situation, for example, an operator conducting the recording might be totally unaware that the tape has been perforated and that the recording circuits have been inhibited.
In contrast, when plugs are used to close the cavity, many of the disadvantages of using tape are avoided. On the other hand, however, plugs are easily lost or misplaced and, in time, may also become loose fitting and drop from a cavity into the interior of a recording apparatus without the knowledge of the operator. As with perforated tape, such an occurrence would result in an undesired inhibiting of the recording circuits and could lead, as with tape, to fouling of the equipment.